1. Field of the Invention
The present invention relates to a signal demultiplexing device and a signal routing device in a high speed transmission system, for time division demultiplexing a series of high speed multiplexed signal lights in which signal lights with a prescribed identical frequency, i.e., identical wavelength, are time division multiplexed in terms of time-slots, by converting them into low speed wavelength division multiplexed signal lights, and outputting signal lights of desired wavelengths that constitute the low speed wavelength division multiplexed signals by distributing them in desired time-slots.
2. Description of the Background Art
A conventional signal demultiplexing device of this type is as shown in FIG. 11, for example. In this conventional signal demultiplexing device of FIG. 11, high speed multiplexed signal lights constituting a series of signal lights that are time division multiplexed in terms of time-slots T1, T2, T3 and T4 are distributed by a distributor 61 and a plurality of distributed signal lights are respectively supplied to a plurality of separators 63a, 63b, 63c and 63d. 
On the other hand, a prescribed phase difference xcex94T corresponding to a time interval between adjacent time-slots is sequentially given by phase difference giving elements 67a, 67b and 67c such as delay lines, with respect to a series of signals sequentially outputted from an oscillator 65, so as to sequentially generate time division demultiplexing signals with phases coinciding with those of the time-slots. This series of time division demultiplexing signals are respectively supplied to the plurality of separators 63d, 63c, 63b and 63a where signal lights of the respective time-slots are extracted by using the time division demultiplexing signals, and the signal lights of the respective time-slots T1, T2, T3 and T4 are received by a plurality of receivers 69a, 69b, 69c and 69d respectively.
The conventional signal demultiplexing device in such a configuration requires a plurality of separators 63a to 63d which are time division demultiplexing elements for the purpose of extracting the respective time-slots, and there is a need to align phases of the respective time-slots with phases at respective separators, while the time-slot demultiplexing speed is limited by the separators 63a to 63d that are the time division demultiplexing elements.
FIG. 2 shows a configuration of a signal demultiplexing device using a wavelength converter. This signal demultiplexing device of FIG. 2 has a wavelength converter 1 into which signal lights with a prescribed identical wavelength xcexs that are high speed time division multiplexed signal lights multiplexed in terms of time-slots T1, T2, T3 and T4 are inputted, and probe lights that are low speed wavelength division multiplexed signal lights comprising a series of sub-probe lights with prescribed different wavelengths xcex1, xcex2, xcex3 and xcex4 for respective time-slots T1, T2, T3 and T4 that are synchronized with the high speed time division multiplexed signal lights are also inputted. In this wavelength converter 1, the prescribed wavelength xcexs of each signal light in each time-slot is converted into a desired wavelength xcexi (i=1, 2, 3, 4) of the probe light in the corresponding time-slot Ti (i=1, 2, 3, 4), and resulting wavelength division multiplexed signal lights are supplied to a wavelength demultiplexer 9.
Then, at the wavelength demultiplexer 9, the wavelength division multiplexed signal lights from the wavelength converter 1 are demultiplexed, and as outputs of the wavelength demultiplexer 9 shown in FIG. 2, a signal light with a wavelength xcex1 is outputted to the time-slot T1 from a first port of the wavelength demultiplexer 9 and received by a receiver 11a, a signal light with a wavelength xcex2 is outputted to the time-slot T2 from a second port of the wavelength demultiplexer 9 and received by a receiver 11b, a signal light with a wavelength xcex3 is outputted to the time-slot T3 from a third port of the wavelength demultiplexer 9 and received by a receiver 11c, and a signal light with a wavelength xcex4 is outputted to the time-slot T4 from a fourth port of the wavelength demultiplexer 9 and received by a receiver 11d. 
Note that the probe lights constituting the low speed wavelength division multiplexed signal lights are applied with a clock modulation at a divided frequency of the high speed time division multiplexed signal lights, and a phase relationship adjustment such that bits are in complementary relationship, thereby converting the high speed time division multiplexed signal lights into the wavelength division multiplexed signal lights which are them wavelength demultiplexed and received by the respective receivers 11a, 11b, 11c and 11d. 
In the signal demultiplexing device using the wavelength converter described above, the probe lights that are low speed signals can be generated conventionally by an individual modulation scheme using electrically generated phase differences, an individual modulation scheme using optically generated phase differences, or a collective modulation scheme, and each of these schemes will be described next.
FIG. 12 shows a circuit configuration of a conventional probe light source for realizing the individual modulation scheme using electrically generated phase difference mentioned above. The probe light source of FIG. 12 has a plurality of sub-probe light sources 13a, 13b, 13c and 13d for respectively generating sub-probe lights with prescribed different wavelengths xcex1, xcex2, xcex3 and xcex4 for respective time-slots T1, T2, T3 and T4, and the sub-probe lights with wavelengths xcex1, xcex2, xcex3 and xcex4 outputted from these sub-probe light sources 13a, 13b, 13c and 13d are respectively supplied to modulators 71a, 71b, 71c and 71d. 
On the other hand, a prescribed phase difference xcex94T corresponding to a time interval between adjacent time-slots is sequentially given by electric phase difference giving elements 67a, 67b and 67c such as delay lines, with respect to a series of signals sequentially outputted from an oscillator 65, so as to sequentially generate phase adjustment signals with phases coinciding with those of the time-slots. This series of phase adjustment signals are supplied to the respective modulators 71a, 71b, 71c and 71d where phases of the sub-probe lights from the sub-probe light sources 13a, 13b, 13c and 13d are adjusted, and the phase adjusted sub-probe lights are multiplexed by a multiplexer 73, and the probe lights comprising a series of sub-probe lights with different wavelengths xcex1, xcex2, xcex3 and xcex4 for the respective time-slots T1, T2, T3 and T4 which are synchronized with the respective time-slots T1, T2, T3 and T4 are outputted from the multiplexer 73.
FIG. 13 shows a circuit configuration of a conventional probe light source for realizing the individual modulation scheme using optically generated phase difference mentioned above. The probe light source of FIG. 13 uses a plurality of optical fibers 75a, 75b, 75c and 75d with different lengths for optically generating phase differences, instead of the electric phase difference giving elements 67a, 67b and 67c used in the conventional probe light source shown in FIG. 12, such that a sub-probe light with a wavelength xcex1 transmitted from the sub-probe light source 13a through the modulator 71a is inputted into the multiplexer 73 without any delay by an optical fiber 75a, a sub-probe light with a wavelength xcex2 transmitted from the sub-probe light source 13b through the modulator 71b is inputted into the multiplexer 73 with a delay of xcex94T by an optical fiber 75b, a sub-probe light with a wavelength xcex3 transmitted from the sub-probe light source 13c through the modulator 71c is inputted into the multiplexer 73 with a delay of 2xcex94T by an optical fiber 75c, and a sub-probe light with a wavelength xcex4 transmitted from the sub-probe light source 13d through the modulator 71d is inputted into the multiplexer 73 with a delay of 3xcex94T by an optical fiber 75d. Then, the probe lights comprising a series of sub-probe lights with different wavelengths xcex1, xcex2, xcex3 and xcex4 for the respective time-slots T1, T2, T3 and T4 are outputted from the multiplexer 73.
FIG. 14 shows a circuit configuration of a conventional probe light source for realizing the collective modulation scheme mentioned above. The probe light source of FIG. 14 multiplexes the sub-probe lights with wavelengths xcex1, xcex2, xcex3 and xcex4 from the plurality of sub-probe light sources 13a, 13b, 13c and 13d at a multiplexer 77, and applies a collective modulation to the multiplexed sub-probe lights at an oscillator driven modulator 79. Then, these sub-probe lights are wavelength demultiplexed at a demultiplexer 81, and necessary phase differences are given to the respective wavelength demultiplexed sub-probe lights by optical fibers 83a, 83b, 83c and 83d. Then, these sub-probe lights are multiplexed at a multiplexer 85, and the probe lights comprising a series of sub-probe lights with different wavelengths xcex1, xcex2, xcex3 and xcex4 for the respective time-slots T1, T2, T3 and T4 are outputted from the multiplexer 85.
Now, the conventional probe light sources used for the signal demultiplexing device using the wavelength converter described above are associated with problems that there is a need to adjust a phase of the optical wavelength signal with respect to the respective time-slot individually, and that there is a possibility for increasing a scale of hardware regarding the wavelength multiplexing and demultiplexing.
It is therefore an object of the present invention to provide a signal demultiplexing device and a signal routing device in a high speed transmission system capable of handling the high speed multiplexed signal lights for which a processing using electric signals is impossible, by using a relatively simple circuit configuration.
According to one aspect of the present invention there is provided a signal demultiplexing device in a high speed transmission system, for time division demultiplexing high speed multiplexed signal lights in which signal lights with a prescribed identical wavelength are time division multiplexed in terms of time-slots, by converting the high speed multiplexed signal lights into low speed wavelength division multiplexed signal lights, the signal demultiplexing device comprising: a probe light source configured to generate probe lights formed by a series of sub-probe lights with prescribed different wavelengths for respective time-slots, in synchronization with the high speed multiplexed signal lights; a wavelength converter configured to receive the probe lights from the probe light source and the high speed multiplexed signal lights, and to convert the prescribed identical wavelength of the high speed multiplexed signal lights in each time-slot into a prescribed wavelength of a probe light in a corresponding time-slot so as to obtain wavelength division multiplexed signal lights; and a wavelength demultiplexer configured to wavelength division demultiplex the wavelength division multiplexed signal lights obtained by the wavelength converter, and to output demultiplexed signal lights; wherein the probe light source has: a plurality of sub-probe light sources configured to respectively generate the sub-probe lights with the prescribed different wavelengths for respective time-slots; a multiplexer configured to multiplex the sub-probe lights generated by the plurality of sub-probe light sources; and a phase different giving unit configured to give phase differences corresponding to time-slot positions to the sub-probe lights multiplexed by the multiplexer, and to sequentially output the sub-probe lights with the phase differences in correspondence to respective time-slots.
According to another aspect of the present invention there is provided a signal routing device in a high speed transmission system, for time division demultiplexing high speed multiplexed signal lights in which signal lights with a prescribed identical wavelength are time division multiplexed in terms of time-slots, by converting the high speed multiplexed signal lights into low speed wavelength division multiplexed signal lights, and for outputting signal lights by distributing signal lights with desired wavelengths that constitute the low speed wavelength division multiplexed signals into desired time-slots according to routing control signals, the signal routing device comprising: a probe light source configured to generate probe lights formed by a series of sub-probe lights with variable desired wavelengths for respective time-slots, in synchronization with the high speed multiplexed signal lights; a wavelength converter configured to receive the probe lights from the probe light source and the high speed multiplexed signal lights, and to convert the prescribed identical wavelength of the high speed multiplexed signal lights in each time-slot into a prescribed wavelength of a probe light in a corresponding time-slot so as to obtain wavelength division multiplexed signal lights; and a wavelength demultiplexer configured to wavelength division demultiplex the wavelength division multiplexed signal lights obtained by the wavelength converter, and to output demultiplexed signal lights; wherein the probe light source has: a plurality of sub-probe light sources configured to respectively generate the sub-probe lights with prescribed different wavelengths for respective time-slots; a multiplexer configured to multiplex the sub-probe lights generated by the plurality of sub-probe light sources; and a phase different giving unit configured to give phase differences corresponding to time-slot positions to the sub-probe lights multiplexed by the multiplexer, and to sequentially output the sub-probe lights with the phase differences in correspondence to respective time-slots, such that a sub-probe light with a desired wavelength is outputted in correspondence to a desired time-slot according to the routing control signals.
Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings.